I have already exposed to this problem during my Philosophical journey.
There are very important questions:
Is it possible that there's nothing but God and me?. Is it a solipsism?.
Could it be a solipsism but for many spirits?, Each mind passes through a specific clear, orderly, coherent and solipsistic dream?. Or it's one dream, takes place in the same time for many minds?.
If we can answer the question: what creation means for God?.It is then so easy to expect what type of world, or worlds are created.
Hindu Philosophy says it is a pastime, sport for God, they call it Lila.
For God to have more sport, pastime, is it pereferable for creation to be a uni-solipsism or many-solipsism or one dream for many souls (minds)?.
Thus we have four possibilities:
1- There's only one world with one mind only=uni-solipsism. That means less pastime, sport for God.
2- There are many worlds, each world having only one mind=many-solipsism.
That means more pastime, sport for God.
3- There's one world having many minds. This means more and more pastime, sport for God.
4- There are many worlds, each world having many minds. This means the highest pastime, sport for God.
But, how did Berkeley justify the existence of other minds?, We can quote from his works as follows:
For Berkeley, we have no direct 'idea' of spirits, albeit we have good reason to believe in the existence of other spirits, for their existence explains the purposeful regularities we find in experience. ("It is plain that we cannot know the existence of other spirits otherwise than by their operations, or the ideas by them excited in us", Dialogues #145). This is the solution that Berkeley offers to the problem of other minds.
So, Subjective Idealism=clear, orderly, coherent Dream.
Justifying other minds=many minds see the same Dream, at the same time.